Imaging compositions and methods

ABSTRACT

Imaging compositions and methods of using the compositions are disclosed. The imaging compositions include two discrete components. One component includes opacifying compounds and the second component includes sensitizing dyes. The second component is sensitive to low levels of energy. Application of the low levels of energy induces a color or shade change in the second component. The imaging compositions may be applied to a work piece to mark it such that it may be modified based on the marks.

This Patent Application is a continuation-in-part of co-pending patentapplication Ser. No. 10/890,507 filed Jul. 12, 2004, which is acontinuation-in-part of co-pending patent applications Ser. Nos.10/773,989, 10/773,990, and 10/773,991 filed Feb. 6, 2004.

The present invention is directed to imaging compositions having twoseparate functional components and methods of using the imagingcompositions. More specifically, the present invention is directed toimaging compositions having two separate functional components where onecomponent is opaque and the second component undergoes a color or shadechange upon exposure to energy at low powers and methods of using theimaging compositions.

There are numerous compositions and methods employed in variousindustries to form images on substrates to mark the substrates. Suchindustries include the paper industry, packaging industry, paintindustry, medical industry, dental industry, electronics industry,textile industry, aeronautical, marine and automotive industries, andthe visual arts.

Imaging or marking also is employed in proofing products, photoresists,soldermasks, printing plates and other photopolymer products. Forexample, U.S. Pat. No. 5,744,280 discloses photoimageable compositionsallegedly capable of forming monochrome and multichrome images, whichhave contrast image properties. The photoimageable compositions includephotooxidants, photosensitizers, photodeactivation compounds anddeuterated leuco compounds. The leuco compounds are aminotriarylmethinecompounds or related compounds in which the methane (central) carbonatom is deuterated to the extant of at least 60% with deuteriumincorporation in place of the corresponding hydridoaminotriaryl-methine. The patent alleges that the deuterated leucocompounds provide for an increased contrast imaging as opposed tocorresponding hydrido leuco compounds. Upon exposure of thephotoimageable compositions to actinic radiation a phototropic responseis elicited.

Laser imaging has lately been attracting attention as a high-speed andefficient marking method and is already put to practical use in someindustries. Many laser imaging techniques involve irradiating onlynecessary areas of substrates with laser light to denature or remove theirradiated area or irradiating a coated substrate with laser light toremove the irradiated coating layer thereby making a contrast betweenthe irradiated area (imaged area) and the non-irradiated area(background).

Using a laser to mark an article such as a semiconductor chip is a fastand economical means of marking. There are, however, certaindisadvantages associated with state-of-the art laser imaging techniquesthat burn the surface to achieve a desired mark. For example, a markburned in a surface by a laser may only be visible at select angles ofincidence to a light source. Further, oils or other contaminantsdeposited on the article surface subsequent to marking may blur or evenobscure the laser mark. Additionally, because the laser actually burnsthe surface of the work piece, for bare die imaging, the associatedburning may damage any underlying structures or internal circuitry or byincreasing internal die temperature beyond acceptable limits. Moreover,where the manufactured part is not produced of a laser reactivematerial, a laser reactive coating applied to the surface of a componentadds expense and may take hours to cure.

Alternatively, laser projectors may be used to project images ontosurfaces. They are used to assist in the positioning of work pieces onwork surfaces. Some systems have been designed to projectthree-dimensional images onto contoured surfaces rather than flatsurfaces. The projected images are used as patterns for manufacturingproducts and to scan an image of the desired location of a ply onpreviously placed plies. Examples of such uses are in the manufacturingof leather products, roof trusses, and airplane fuselages. Laserprojectors are also used for locating templates or paint masks duringthe painting of aircraft.

The use of scanned laser images to provide an indication of where toplace or align work piece parts, for drilling holes, for forming anoutline for painting a logo or picture, or aligning segments of a marinevessel for gluing requires extreme accuracy in calibrating the positionof the laser projector relative to the work surface. Typically sixreference points are required for sufficient accuracy to align workpiece parts. Reflectors or sensors are positioned in an approximate areawhere the ply is to be placed. Since the points are at fixed locationsrelative to the work and the laser, the laser also knows where it isrelative to the work. Typically, workers hand mark the place where thelaser beam image contacts the work piece with a marker or masking tapeto define the laser image. Such methods are tedious, and the workers'hands may block the laser image disrupting the alignment beam to thework piece. Accordingly, misalignment may occur.

Another problem associated with laser imaging is the potential foropthalmological damage to the workers. Many lasers used in marking maycause retinal damage to workers. Generally, lasers, which generateenergy exceeding 5 mW present hazards to workers.

The inventors of the present invention have addressed the problemsassociated with laser imaging by formulating compositions which changecolor or shade by applying energy at powers of 5 mW or less.Applications of such compositions eliminate the problems associated withhand marking the places on a work piece where the laser is directed andat the same time the use of a low power laser eliminates the potentialof opthalmological damage to workers.

In the applications of such compositions a color or shade contrast isdesired between the compositions and the work pieces such that theworkers may readily distinguish between the work piece and the coloredcompositions to accurately modify the work piece. The greater the coloror shade contrast from the work piece the easier it is for the workersto see the markings and more rapidly and accurately modify the workpiece. This is especially important in assembly line operations wherespeed and accuracy are critical to optimum product output. However, whena work piece is of a similar color or shade as the color or shade of themarkings, workers find it difficult to accurately locate the markings onthe work piece. Accordingly, speed and accuracy are compromised, and theefficiency of the manufacturing process is hindered.

The imaging compositions are not always applied to a bare work piece.Often the imaging compositions are applied to work pieces which havebeen previously treated or coated by various types of chemicalcompositions. The inventors have discovered that such coatings may causedye compounds of the imaging compositions to leach out into the coatingsand cause undesired chemical reactions which result in the formation ofunwanted color changes. Such color changes readily interfere with thedesired color or shade contrast between the marks on the imagingcompositions and the work pieces and workers are unable to perform theirtask. For example, airplane bodies are often coated with an epoxy primermaterial prior to applying paint or any additional coatings to thebodies. When the imaging compositions are applied to such airplanebodies, the dyes in the imaging compositions leach into the epoxyprimers and turn the airplane bodies an undesired red.

Accordingly, there is still a need for improved imaging compositions formarking a work piece.

Imaging compositions include a first component including one or moreopacifying compounds, and a second component including one or moresensitizers. The first component of the imaging compositions inhibitsthe leaching of compounds from the second component into coatings onwork pieces on which the imaging compositions are applied. The firstcomponent also provides a color or shade contrast between the secondcomponent of the imaging compositions and the work pieces. The secondcomponent may be imaged by exposing the compositions to energy levels of5 mW or less.

In another aspect the imaging compositions include a first componentincluding one or more opacifying compounds and one or more releaseagents, and a second component including one or more sensitizers and oneor more release agents.

The imaging compositions also may include one or more film formingpolymers, adhesives, plasticizers, flow agents, chain transfer agents,organic acids, accelerators, surfactants, thickeners, monomers, rheologymodifiers, release agents, diluents and other optional components totailor the compositions for a particular imaging method and work piece.The imaging compositions may be applied to a work piece to form an imageon the work piece for workers to modify the work piece to make anarticle.

In a further aspect methods of imaging include providing a firstcomponent of a composition including one or more opacifying compounds;applying the first component of the composition to a work piece;providing a second component of the composition including one or moresensitizers; applying the second component of the composition on thefirst component; exposing the composition to energy at powers of 5 mW orless to affect a color or shade change in the second component; andexecuting a task on the work piece as directed by the color or shadechange of the second component of the composition to modify the workpiece. The energy may be applied selectively to form an imaged patternon the work piece.

The image may be used as a mark to drill holes for fasteners, to joinparts together, to align segments of parts, and to form an outline formaking a logo or picture on articles such as terrestrial vehicles,aeronautical ships, marine vessels, terrestrial structures and textiles.Since the compositions may be promptly applied to the work piece and theimage promptly formed by application of energy at intensities of 5 mW orless to create a color or shade contrast, workers no longer need to beadjacent the work piece to mark laser beam images with a hand-heldmarker or tape in the fabrication of articles. Accordingly, the problemsof blocking light caused by the movement of workers hands and the slowerand tedious process of applying marks by workers using a hand-heldmarker or tape is eliminated. Further, the low powers of energy, whichare used to cause the color or shade change, eliminate or at leastreduce the potential for opthalmological damage to workers.

The imaging compositions may be applied to the work piece by methodswhich include, but are not limited to, spray coating, brushing, rollercoating, ink jetting, dipping and immersion. Energy sources for applyinga sufficient amount of energy to create the color or shade changeinclude laser, infrared and ultraviolet light generating devices andapparatus.

In one aspect the imaging compositions are peelable from the work pieceavoiding the use of undesirable solvents or developers. Such solventsand developers may be carcinogenic and potentially contaminate theenvironment, thus costly waste treatment is used to reduce environmentalpollution. Accordingly, the imaging compositions provide for moreefficient manufacturing than many conventional alignment and imagingprocesses, and also may reduce the amount of waste treatment.

As used throughout this specification, the following abbreviations havethe following meaning, unless the context indicates otherwise: °C.=degrees Centigarde; IR=infrared; UV=ultraviolet; gm=gram;mg=milligram; L=liter; mL=milliliter; wt %=weight percent; erg=1 dynecm=10⁻⁷ joules; J=joule; mJ=millijoule; nm=nanometer=10⁻⁹ meters;cm=centimeters; mm=millimeters; W=watt=1 joule/second; and mW=milliwatt;ns=nanosecond; μsec=microsecond; Hz=hertz; μm=microns; and T_(g)=glasstransition temperature; Δ=delta=mathematical symbol designating a changein a variable.

The terms “polymer” and “copolymer” are used interchangeably throughoutthis specification. “Actinic radiation” means radiation from light thatproduces a chemical change. “Photofugitive response” means that theapplication of energy causes a colored material to fade or becomelighter. “Phototropic response” means that the application of energycauses material to darken. “Changing shade” means that the color fades,or becomes darker. “(Meth)acrylate” includes both methacrylate andacrylate, and “(meth)acrylic acid” includes both methacrylic acid andacrylic acid. “Diluent” means a carrier or vehicle, such as solvents orsolid fillers. “Opacity” means the property of being impervious to lightrays, i.e. not transparent or translucent. “Opaque” means nontransparentand nontranslucent. “Translucent” means semitransparent. “Transparent”means a passage of rays of the visible spectrum.

Unless otherwise noted, all percentages are by weight and are based ondry weight or solvent free weight. All numerical ranges are inclusiveand combinable in any order, except where it is logical that suchnumerical ranges are constrained to add up to 100%.

Imaging compositions include a first component including one or moreopacifying compounds, and a second component including one or moresensitizers. The first component of the imaging compositions inhibitsleaching of compounds from the second component into coatings on workpieces on which the imaging compositions are applied. The firstcomponent also provides a color or shade contrast between the secondcomponent of the imaging compositions and the work pieces. Further,including one or more opacifying compounds in the first component,increases the rate of color or shade change of the second component. Thesecond component may be imaged by exposing the compositions to energylevels of 5 mW or less.

The first component including one or more opacifying compounds isapplied to the work piece. The first component is dried then the secondcomponent including the one or more sensitizers is applied on the driedfirst component. The second component is then dried and the imagingcomposition is then imaged with energy at 5 mW or less. Workers thenmodify the work piece based on the imaged composition. The compositionmay be removed from the work piece by any suitable method. Typically,the composition is peeled from the work piece.

Often a work piece may be sufficiently dark in color or shade such as toreduce the contrast between the imaged second component and the workpiece, thus compromising accurate modification of the work piece.Including opacifying compounds in the second component causes areflection of a portion of the applied energy, thus requiring longerexposure times to affect the color or shade change. By including theopacifying compounds in the first component, faster color and shadechanges are achieved in the second component.

The imaging compositions may be applied to a work piece by any suitablemethod including, but not limited to, spraying, brushing, rollercoating, ink jetting, dipping and immersion. The compositions may beremoved from the work piece by any suitable method such as with adeveloper, stripper or by peeling the unwanted portions from workpieces. Typically, the compositions are peeled by hand or by using asuitable device or apparatus known in the art such as a knife orscrapper. Peelable compositions avoid the use of environmentallyhazardous solvents and developers, and reduce the amount of waste.

Any suitable opacifying compound which provides a desired color or shadecontrast between the second component and the work piece may be used.Such compounds are used in the first component in amounts of 1 wt % to80 wt %, or such as from 5 wt % to 50 wt %, or such as 10 wt % to 20 wt%.

Opacifying compounds include, but are not limited to, pigments(inorganic and organic), metal salts, silica, silicates and clays.Organic pigments include, but are not limited to, indigo,phthalocyanine, para red and flavanoids such as red, yellow, blue,orange and ivory colors. Inorganic pigments include, but are not limitedto, oxides such as titanium dioxide, zirconium oxide, ceric oxide,antimony trioxide, arsenic pentoxide, aluminum oxide, zinc oxide, cobaltoxide, cadmium oxide, chromium oxide, magnesium oxide, iron oxide andlead oxide. Also, mixed phase titanates and mixed phase oxides may beincluded. Metal salts include, but are not limited to, sulfides,sulfates, carbonates and hydroxides. Typically, the opacifying compoundsare inorganic pigments. More typically, the opacifying compounds areinorganic pigments such as titanium dioxide, aluminum oxide, zinc oxideand silicates. Most typically the opacifying compounds are inorganicpigments such as titanium dioxide, aluminum oxide and zinc oxide. Theopacifying compounds have an average size of 0.01 μm to 10 μm, or suchas from 0.5 μm to 5 μm, or such as from 1 μm to 3 μm.

In addition to the opacifying agents, the first component may include,but is not limited to, one or more additives such as film formingpolymers, diluents, thickeners, rheology modifiers, adhesives,plasticizers, flow agents, organic acids, surfactants and release agentsto tailor the first component for compatibility with the secondcomponent and the work piece. Typically, such additives are included inthe first component as in the second component.

Film forming polymers are included in the first component to function asbinders. Any film forming polymer may be employed in the first componentprovided the polymers do not cause the opacifying agents to agglomerateor concentrate out of the first component. Suitable film formingpolymers for the first component include, but are not limited to, thefilm forming polymers described below for the second component. The filmforming polymers are included in the first component in amounts from 10wt % to 95 wt %, or such as from 15 wt % to 80 wt %, or such as from 25wt % to 65 wt % of the first component.

Optionally, an adhesive may be included in the first component. Theadhesive may be a permanent adhesive, a semi-permanent, a repositionableadhesive, a releasable adhesive, or freezer category adhesive. Many suchadhesives may be classified as hot-melt, hot-melt pressure sensitive,and pressure sensitive adhesives. Typically, the releasable adhesivesare pressure sensitive adhesives. Typically, releasable, pressuresensitive adhesives are used. Such releasable, pressure sensitiveadhesives include, but are not limited to, acrylics, polyurethanes,poly-alpha-olefins, silicones, combinations of acrylate pressuresensitive adhesives and thermoplastic elastomer-based pressure sensitiveadhesives, and tackified and natural rubbers. Adhesives may be includedin the first component in amounts of from 0.5 wt % to 15 wt %, or suchas from 5 wt % to 10 wt % of the first component.

One or more amphoteric surfactants may be included in the firstcomponent to act as release agents such that the imaging compositionsmay be readily peeled from a work piece. Suitable amphoteric surfactantsinclude those described below for the second component of the imagingcompositions. The amphoteric surfactants are included in the firstcomponent in the same amounts as in the second component.

One or more diluents may be included in the first component. Suchdiluents include, but are not limited to, water and organic solvents.Examples of suitable organic solvents are described below for the secondcomponent of the imaging compositions.

Sensitizers employed in the second component are compounds which areactivated by energy to change color or shade, or upon activation causeone or more other compounds to change color or shade. The secondcomponent includes one or more photosensitizers activated by visiblelight energy at powers of 5 mW or less. Generally, such sensitizers areincluded in amounts of from 0.005 wt % to 10 wt %, or such as from 0.05wt % to 5 wt %, or such as from 0.1 wt % to 1 wt % of the secondcomponent.

Sensitizers, which are activated in the visible range, typically areactivated at wavelengths of from above 300 nm to less than 600 nm, orsuch as from 350 nm to 550 nm, or such as from 400 nm to 535 nm. Suchsensitizers include, but are not limited to, xanthene compounds andcyclopentanone based conjugated compounds.

Suitable xanthene compounds include, but are not limited to, compoundshaving the general formula:

where X is hydrogen, sodium ion, or potassium ion; Y is hydrogen, sodiumion, potassium ion or —C₂H₅; R₁ is hydrogen, Cl⁻, Br⁻, or I⁻; R₂ ishydrogen, Cl⁻, Br⁻, or I⁻; R₃ is hydrogen, Cl⁻, Br⁻, I⁻, or —NO₂; R₄ ishydrogen, —NO₂, Cl⁻, Br⁻, or I⁻; R₅ is hydrogen, Cl⁻ or Br⁻; R₆ ishydrogen, Cl⁻, or Br⁻; R₆ is hydrogen, Cl⁻, or Br⁻; R₇ is hydrogen, Cl⁻,or Br⁻; and R₈ is hydrogen, Cl⁻, or Br⁻.

Examples of such xanthene compounds are compounds such as fluoresceinand derivatives thereof such as the halogenated xanthenes such as2′,4′,5′,7′-tetrabromo-3,4,5,6-tetrachlorofluorescein (phloxin B),2′,4′,5′,7′-tetraiodofluorescein (erythrosin, erythrosin B, or C.I. AcidRed 51), 2′,4′,5′,7′-tetraiodo-3,4,5,6-tetrachlorofluorescein (RoseBengal), 2′,4′,5′,7′,3,4,5,6-octabromofluorescein(octabromofluorescein), 4,5,6,7-tetrabromoerythrosin,4′,5′-dichlorofluorescein, 2′,7′-dichlorofluorescein,4,5,6,7-tetrachlorofluorescein, 2′,4′,5′,7′-tetrachlorofluorescein,dibromofluorescein, Solvent Red 72, diiodofluorescein, eosin B, eosin Y,ethyl eosin, and salts thereof. Typically, the salts are alkali metalsalts such as the sodium and potassium salts. Such xanthene compoundstypically are used in amounts of from 0.05 wt % to 2 wt %, or such asfrom 0.25 wt % to 1 wt %, or such as from 0.1 wt % to 0.5 wt % of thecomposition.

Examples of suitable cyclopentanone based conjugated compounds arecyclopentanone, 2,5-bis-[4-(diethylamino)phenyl]methylene]-,cyclopentanone,2,5-bis[(2,3,6,7-tetrahydro-1H,5H-benzo[i,j]quinolizin-9-yl)methylene]-,and cyclopentanone,2,5-bis-[4-(diethyl-amino)-2-methylphenyl]methylene]-. Suchcyclopentanones may be prepared from cyclic ketones and tricyclicaminoaldehydes by methods known in the art.

Examples of such suitable conjugated cyclopentanones have the followingformula:

where p and q independently are 0 or 1, r is 2 or 3; and R₉ isindependently hydrogen, linear or branched (C₁-C₁₀)aliphatic, or linearor branched (C₁-C₁₀)alkoxy, typically R₉ is independently hydrogen,methyl or methoxy; R₁₀ is independently hydrogen, linear or branched(C₁-C₁₀)aliphatic, (C₅-C₇)ring, such as an alicyclic ring, alkaryl,phenyl, linear or branched (C₁-C₁₀)hydroxyalkyl, linear or branchedhydroxy terminated ether, such as —(CH₂)_(v)—O—(CHR₂₀)_(w)—OH, where vis an integer of from 2 to 4, w is an integer of from 1 to 4, and R₂₀ ishydrogen or methyl and carbons of each R₁₀ may be taken together to forma 5 to 7 membered ring with the nitrogen, or a 5 to 7 membered ring withthe nitrogen and with another heteroatom chosen from oxygen, sulfur, anda second nitrogen. Such sensitizers may be activated at powers of 5 mWor less.

Other sensitizers which are activated in the visible light rangeinclude, but are not limited to, N-alkylamino aryl ketones such asbis(9-julolidyl ketone),bis-(N-ethyl-1,2,3,4-tetrahydro-6-quinolyl)ketone andp-methoxyphenyl-(N-ethyl-1,2,3,4-tetrahydro-6-quinolyl)ketone; visiblelight absorbing dyes prepared by base catalyzed condensation of analdehyde or dimethinehemicyanine with the corresponding ketone; visiblelight absorbing squarylium compounds; 1,3-dihydro-1-oxo-2H-indenederivatives; any of the coumarin based dyes which include, but are notlimited to, ketocoumarin, and 3,3′-carbonyl bis(7-diethylaminocoumarin),coumarin 6, coumarin 7, coumarin 99, coumarin 314 and dimethoxy coumarin99; halogenated titanocene compounds such asbis(eta.5-2,4-cyclopentadien-1-yl)-bis(2,6-difluro-3-(1H-pyrrol-1-yl)-phenyl)titanium; and compounds derived from aryl ketones andp-dialkylaminoarylaldehydes. Methods of making the foregoing sensitizersare known in the art or disclosed in the literature. Also, many arecommercially available.

Optionally, the second component may include one or morephotosensitizers that are activated by UV light. Such sensitizers whichare activated by UV light are typically activated at wavelengths of fromabove 10 nm to less than 300 nm, or such as from 50 nm to 250 nm, orsuch as from 100 nm to 200 nm. Such UV activated sensitizers include,but are not limited to, polymeric sensitizers having a weight averagemolecular weight of from 10,000 to 300,000 such as polymers of1-[4-(dimethylamino)phenyl]-1-(4-methoxyphenyl)-methanone,1-[4-(dimethylamino)phenyl]-1-(4-hydroxyphenyl)-methanone and1-[4-(dimethylamino)phenyl]-1-[4-(2-hydroxyethoxy)-phenyl]-methanone;free bases of ketone imine dyestuffs; amino derivatives oftriarylmethane dyestuffs; amino derivatives of xanthene dyestuffs; aminoderivatives of acridine dyestuffs; methine dyestuffs; and polymethinedyestuffs. Methods of preparing such compounds are known in the art.Typically, such UV activated sensitizers are used in amounts of from0.05 wt % to 1 wt %, or such as from 0.1 wt % to 0.5 wt % of the secondcomponent.

Optionally, the second component may include one or morephotosensitizers that are activated by IR light. Such sensitizers whichare activated by IR light are typically activated at wavelengths of fromgreater than 600 nm to less than 1,000 nm, or such as from 700 nm to 900nm, or such as from 750 nm to 850 nm. Such IR activated sensitizersinclude, but are not limited to, infrared squarylium dyes, andcarbocyanine dyes. Such dyes are known in the art and may be made bymethods described in the literature. Typically, such dyes are includedin the compositions in amounts of from 0.05 wt % to 3 wt %, or such asfrom 0.5 wt % to 2 wt %, or such as from 0.1wt % to 1 wt % of the secondcomponent.

Photoreducing agents also may be used in the second component. Compoundswhich may function as photoreducing agents include, but are not limitedto, one or more quinone compounds such as pyrenequinones such as1,6-pyrenequinone and 1,8-pyrenequinone; 9,10-anthrquinone,1-chloroanthraquinone, 2-chloro-anthraquinone, 2-methylanthrquinone,2-ethylanthraquinone, 2-tert-butylanthraquinone,octamethylanthraquinone, 1,4-naphthoquinone, 9,10-phenanthrenequinone,1,2-benzaanthrquinone, 2,3-benzanthraquinone,2-methyl-1,4-naphthoquinone, 2,3-dichloronaphthoquinone,1,4-dimethylanthraquinone, 2,3-dimethylanthraquinone, sodium salt ofanthraquinone alpha-sulfonic acid, 3-chloro-2-methylanthraquinone,retenequinone, 7,8,9,10-tetrahydronaphthacenequinone, and1,2,3,4-tetrahydrobenz(a)anthracene-7,12-dione.

Other compounds which may function as photoreducing agents include, butare not limited to, acyl esters of triethanolamines having a formula:N(CH₂CH₂OC(O)—R₁₁)₃   (III)where R₁₁ is alkyl of 1 to 4 carbon atoms, and 0 to 99% of a C₁ to C₄alkyl ester of nitrilotriacetic acid or of 3,3′,3″-nitrilotripropionicacid. Examples of such acyl esters of triethanolamine aretriethanolamine triacetate and dibenzylethanolamine acetate.

One or more photoreducing agent may be used in the second component toprovide the desired color or shade change. Typically, one or morequinone is used with one or more acyl ester of triethanolamine toprovide the desired reducing agent function. Photoreducing agents may beused in the compositions in amounts of from 0.05 wt % to 50 wt %, orsuch as from 5 wt % to 40 wt %, or such as 20 wt % to 35 wt %.

Suitable color formers in the second component include, but are notlimited to, leuco-type compounds. Such leuco-type compounds include, butare not limited to, aminotriarylmethanes, aminoxanthenes,aminothioxanthenes, amino-9,10-dihydroacridines, aminophenoxazines,aminophenothiazines, aminodihydrophenazines, antinodiphenylmethines,leuco indamines, aminohydrocinnamic acids such as cyanoethanes and leucomethines, hydrazines, leuco indigoid dyes,amino-2,3-dihydroanthraquinones, tetrahalo-p,p′-biphenols,2(p-hydroxyphenyl)-4,5-diphenylimidazoles, and phenethylanilines.Typically, the aminotriarylmethane leuco dyes, such as the o-methylsubstituted dyes, are used. The o-methyl substitution is believed tomake the structure non-planar and more resistant to oxidation than manyother leuco-type dyes. Color formers are included in amounts of from 0.1wt % to 5 wt %, or such as from 0.25 wt % to 3 wt %, or such as from 0.5wt % to 2 wt % of the second component.

Oxidizing agents also may be included in the second component toinfluence the color or shade change. Typically such oxidizing agents areused in combination with one or more color formers. Compounds, which mayfunction as oxidizing agents include, but are not limited to,hexaarylbiimidazole compounds such as2,4,5,2′,4′,5′-hexaphenylbiimidazole,2,2′,5-tris(2-chlorophenyl)-4-(3,4-dimethoxyphenyl)-4,5-diphenylbiimidazole(and isomers),2,2′-bis(2-ethoxyphenyl)-4,4′,5,5′,-tetraphenyl-1,1′-bi-1H-mimidazole,and 2,2′-di-1-naphthalenyl-4,4′,5,5′-tetraphenyl-1′-bi-1H-imidazole.Other suitable compounds include, but are not limited to, halogenatedcompounds with a bond dissociation energy to produce a first halogen asa free radical of not less than 40 kilocalories per mole, and having notmore than one hydrogen attached thereto; a sulfonyl halide having aformula: R′—SO₂—X′ where R′ is an alkyl, alkenyl, cycloalkyl, aryl,alkaryl, or aralkyl and X′ is chlorine or bromine; a sulfenyl halide ofthe formula: R″—S—X″ where R″ and X″ have the same meaning as R′ and X′above; tetraaryl hydrazines, benzothiazolyl disulfides,polymetharylaldehydes, alkylidene 2,5-cyclohexadien-1-ones, azobenzyls,nitrosos, alkyl (T1), peroxides, and haloamines. Typical examples ofsuitable halogenated sulfones include tribromomethyl aryl sulfones suchas tribromomethylphenyl sulfone, tribromomethyl p-tolyl sulfone,tribromomethyl 4-chlorophenyl sulfone, tribromomethyl 4-bromophenylsulfone, and tribromomethyl phenyl sulfone. Such compounds are includedin the second component in amounts of from 0.25 wt % to 10 wt %, or suchas from 0.5 wt % to 5 wt %, or such as from 1 wt % to 3 wt %. Methodsare known in the art for preparing the compounds and many arecommercially available.

Film forming polymers may be included in the second component tofunction as binders. Any film forming binder may be employed providedthat the film forming polymers do not adversely interfere with thedesired color or shade change, and have a T_(g) of from −60° C. togreater than 80° C. or such as from −60° C. to 80° C., or such as fromgreater than −60° C. to greater than 40° C., or such as from 0° C. to35° C. The film forming polymers are included in amounts of from 10 wt %to 90 wt %, or such as from 15 wt % to 70 wt %, or such as from 25 wt %to 60 wt %. Typically, the film forming polymers are derived from amixture of acid functional monomers and non-acid functional monomers.Suitable acid functional monomers include, but are not limited to,(meth)acrylic acid, maleic acid, fumaric acid, citraconic acid,2-acrylamido-2-methylpropanesulfonic acid, 2-hydroxyethyl acrylolphosphate, 2-hydroxypropyl acrylol phosphate, and2-hydroxy-alpha-acrylol phosphate.

Suitable non-acid functional monomers include, but are not limited to,esters of (meth)acrylic acid such as methyl acrylate, 2-ethyl hexylacrylate, n-butyl acrylate, n-hexyl acrylate, methyl methacrylate,hydroxyl ethyl acrylate, butyl methacrylate, octyl acrylate, 2-ethoxyethyl methacrylate, t-butyl acrylate, 1,5-pentanediol diacrylate,N,N-diethylaminoethyl acrylate, ethylene glycol diacrylate,1,3-propanediol diacrylate, decamethylene glycol diacrylate,decamethylene glycol dimethacrylate, 1,4-cyclohexanediol diacrylate,2,2-dimethyylol propane diacrylate, glycerol diacrylate, tripropyleneglycol diacrylate, glycerol triacrylate, 2,2-di(p-hydroxyphenyl)-propanedimethacrylate, triethylene glycol diacrylate,polyoxyethyl-2,2-di(p-hydroxyphenyl)-propane dimethacrylate, triethyleneglycol dimethacrylate, polyoxypropyltrimethylol propane triacrylate,ethylene glycol dimethacrylate, butylenes glycol dimethacrylate,1,3-propanediol dimethacrylate, 1,2,4-butanetriol trimethacrylate,2,2,4-trimethyl-1,3-pentanediol dimethacrylate, pentaerythritoltrimethacrylate, 1-phenyl ethylene-1,2-dimethacrylate, pentaerythritoltetramethacrylate, trimethylol propane trimethacrylate, 1,5-pentanedioldimethacrylate; styrene and substituted styrene such as 2-methyl styreneand vinyl toluene and vinyl esters such as vinyl acrylate and vinylmethacrylate.

When the film forming polymer has a T_(g) of −60° C. to 0° C., the filmforming polymers typically have from 0.1 wt % to 6 wt % of the totalweight of the polymer at least one carboxy functional monomer, or suchas from 0.5 wt % to 6 wt %, or such as from 1 wt % to 5 wt % of at leastone carboxy functional monomer. When the film forming polymer has aT_(g) of greater than 0° C. to greater than 80° C., and one or morebases are included in the composition to maintain a pH range of 3 to 11or such as from 8 to 11, the polymer may optionally include, aspolymerized units, carboxy functional monomers in amounts of from 0.1 wt% to 6 wt %, based on the total weight of the dry film forming polymer,or such as from 0.5 wt % to 6 wt %, or such as from 0.1 wt % to 5 wt %of the total weight of the dry film forming polymer.

Other suitable polymers include, but are not limited to, nonionicpolymers such as polyvinyl alcohol, polyvinyl pyrrolidone,hydroxyl-ethylcellulose, and hydroxyethylpropyl methylcellulose. Alsopolymers such as polyvinyl acetate may be used.

Amphoteric surfactants may be included in the second component tofunction as release agents such that the compositions may be peeled froma work piece. Such surfactants also stabilize particles of the polymersduring and after aqueous emulsion polymerization, or other dispersionpolymerizations. Suitable amphoteric surfactants are those which haveweakly acidic functionalities such as carboxy functionalities, and haveisoelectric points of from pH 3 to pH 8. Such amphoteric surfactants maybe included in the second component in amounts of from 0.1 wt % to 6 wt%, or such as from 0.25 wt % to 5 wt %, or such as from 0.5 wt % to 4 wt% of the film forming binder polymer. Such amphoteric surfactantsinclude, but are not limited to, amino carboxylic acids, amphotericimidazoline derivatives, betaine, fluorocarbon and siloxane versionsthereof, macromolecular amphoteric surfactants and mixtures thereof.

Any of the aminocarboxylic acids may have carboxy moieties present ineither protonated form or in carboxylate form. Where more than onecarboxy group is present on a molecule, those carboxy groups may all bein protonated form, in carboxylate form, or they may be present as somemixture of protonated and carboxylate forms. Furthermore, the ratio ofprotonated to unprotonated carboxy moieties may vary from one moleculeto another, otherwise identical, molecule in a given system. Cationspresent as counter ions for the carboxylate moieties include cations oflithium, sodium, potassium, amines (i.e., ammonium cations derived fromprotonation or other quaternary substitution of amines), zinc,zirconium, calcium, magnesium, and aluminum. Any of the aminocarboxylicacids may have amino moieties present in either protonated (ammonium) orfree amine form (i.e., as deprotonated primary, secondary, or tertiaryamine). Where more than one amino group is present on a molecule, thoseamino groups may all be in protonated form, in free amine form, or theymay be present as some mixture of protonated and free amine forms.Again, the ratio of protonated to unprotonated amine moieties may varyfrom one molecule to another, otherwise identical, molecule in a givensystem. Anions present as counter ions for the ammonium moieties includechloride, bromide, sulfate, carbonate, hydroxide, formate, acetate,propionate and other carboxylate anions.

Suitable aminocarboxylic acids include, but are not limited to:α-aminocarboxylic acids having the general formula R₁₂—NH—CH₂COOH, whereR₁₂═C₄-C₂₀ linear or branched, alkyl, alkenyl, or fluoro or siliconefunctional hydrophobe group; and β-aminocarboxylic acids having thegeneral structures: R₁₂—NH—CH₂CH₂COOH and R₁₂N(CH₂CH₂COOH)₂, whereR₁₂═C₄-C₂₀ linear or branched, alkyl, alkenyl, or fluoro or siliconefunctional hydrophobe group, β-aminocarboxylic acids are available fromHenkel Corporation, King of Prussia, Pa., under the name DERIPHAT™.Unless otherwise stated, the DERIPHAT™ ampholytes have the generalformula R₁₃—NHCH₂CH₂COOH, where R₁₃=residue of coconut fatty acids,residue of tallow fatty acids, lauric acid, myristic acid, oleic acid,palmitic acid, stearic acid, linoleic acid, other C₄-C₂₀ linear orbranched, alkyl, alkenyl, and mixtures thereof DERIPHAT™ ampholytesuseful in the present invention include: sodium-N-coco-β-aminopropionate(DERIPHAT™ 151, flake 97% active); N-coco-β-aminopropionic acid(DERPHAT™ 151C, 42% solution in water);N-lauryl/myristyl-β-aminopropionic acid (DERIPHAT™ 17° C., 50% inwater); disodium-N-tallow-β-iminodipropionate, R₁₄N(CH₂CH₂COONa)₂,(DERIPHAT™ 154, flake 97% active); disodium-N-lauryl-β-iminodipropionate(DERIPHAT™ 160, flake 97% active); and partial sodium salt ofN-lauryl-β-iminodipropionic acid, R₁₄N(CH₂CH₂COOH)(CH₂CH₂COONa),(DERIPHAT™ 16° C., 30% in water). Useful polyaminocarboxylic acidsinclude R₁₄C(═O)NHC₂H₄(NHC₂H₄)_(y)NHCH₂COOH and R₁₄-substitutedethylenediaminetetraacetic acid (EDTA), where R₁₄═C₄-C₂₀ linear orbranched, alkyl or alkenyl, and y=0−3.

Amphoteric imidazoline derivatives useful include those derived fromvariously substituted 2-alkyl-2-imidazolines and2-alkenyl-2-imidazolines which have nitrogen atoms at the 1 and 3positions of the five-membered ring and a double bond in the 2,3position. The alkyl or alkenyl group may be a C₄-C₂₀ linear or branchedchain. The amphoteric imidazoline derivatives are produced via reactionsin which the imidazoline ring opens hydrolytically under conditionsallowing further reaction with such alkylating agents as sodiumchloroacetate, methyl (meth)acrylate, ethyl (meth)acrylate, and(meth)acrylic acid. Useful amphoteric surfactants derived from thereaction of 1-(2-hydroxyethyl)-2-(R₁)-2-imidazolines with acrylic acidor acrylic acid esters, where R₁₅=residue of coconut fatty acids, are:

cocoamphopropionate, R₁₅—(═O)NHCH₂CH₂N(CH₂CH₂OH)(CH₂CH₂COONa);

cocoamphocarboxypropionic acid,R₁₅—C(═O)NHCH₂CH₂N(CH₂CH₂COOH)(CH₂CH₂CH₂CH₂COOH);

cocoamphocarboxypropionate,R₁₅—C(═O)NHCH₂CH₂N(CH₂CH₂COONa)(CH₂CH₂CH₂CH₂COONa);

cocoamphoglycinate, R₁₅—(═O)NHCH₂CH₂N(CH2CH₂OH)(CH₂COONa); and

cocoamphocarboxyglycinate,[R₅—C(═O)NHCH₂CH₂N⁺(CH₂CH₂OH)(CH₂COONa)₂OH⁻.

Surface-active inner salts containing at least one quaternary ammoniumcation and at least one carboxy anion are called betaines. Thenomenclature for betaines derives from the single compound(trimethylammonio)acetate which is called betaine and exists as an innersalt. Betaines useful as amphoteric surfactants in the claimed inventioninclude compounds of the general formulae: R₁₆N⁺(CH₃)₂CH₂COO⁻;R₁₆CONHCH₂CH₂CH₂N⁺(CH₃)₂COO⁻; and R₁₆—O—CH₂—N⁺(CH₃)₂CH₂COO⁻, whereR₁₆═C₄-C₂₀ linear or branched, alkyl, alkenyl, or fluoro or siliconefunctional hydrophobe group. Specific examples of betaines includeN-dodecyl-N,N-dimethylglycine and cocamidopropyl betaine and (MONATERIC™CAB available from Mona Industries).

Typically, when fluorocarbon substituents are attached to amphotericsurfactants, those substituents are perfluoroalky groups, branched orunbranched, having 6 to 18 carbon atoms. However, these substituents mayinstead be partially fluorinated. They may also bear aryl functionality.Examples of fluorocarbon amphoteric surfactants include fluorinatedalkyl FLUORAD™ FC100 and fluorinated alkyl ZONYL™ FSK, produced by 3Mand Dupont, respectively.

Typical siloxane functional amphoteric surfactants have, for example,the structures:

wherein R₁₇ represents an amphoteric moiety and m+n=3 to 50. An exampleis the polyalkyl betaine polysiloxane copolymer ABIL™ B9950 availablefrom Goldschmidt Chemical Corporation.

Macromolecular amphoteric surfactants useful in the claimed inventioninclude: proteins, protein hydrolysates, derivatives of proteinhydrolysates, starch derivatives, and synthetic amphoteric oligomers andpolymers. Of particular utility are those macromolecular ampholytesbearing carboxy functionality.

Typically the imaging compositions are within a pH range of from 3 to 11or such as from 4 to 7. Optionally, a base may be employed to maintainthe desired pH. To assist in maintaining the second component within adesired pH range, any suitable base may be used. Examples of such basesinclude calcium carbonate, zinc oxide, magnesium oxide, calciumhydroxide or mixtures thereof. Bases are present in the imagingcompositions in amounts of greater than 0.2 moles/100 gm of polymer to 2moles/100 gm of polymer, or such as from 0.3 moles/100 gm of polymer to1.75 moles/100 gm of polymer, or such as from 0.4 moles/100 gm ofpolymer to 1.5 moles/100 gm of polymer.

Optionally, polyvalent metal cations may be included to form an ionicbond with a carboxylic acid group on one or more of the monomers whichcompose the polymers. Any suitable polyvalent cation may be used whichforms an ionic bond with the carboxylic acid groups to achievecross-linking. Such cations include, but are not limited to, Mg²⁺, Sr²⁺,Ba²⁺, Ca²⁺, Zn²⁺, Al³⁺, Zr⁴⁺ or mixtures thereof. Such polyvalentcations are included in the imaging compositions in amounts of 0.001 to0.1 moles/100 gm of dry polymer, or such as from 0.01 to 0.08 moles/100gm of dry polymer, or such as from 0.02 to 0.05 moles/100 gm of drypolymer.

When one or more bases containing polyvalent cations are included incombination with another source of polyvalent cations, the sum of theamounts of base and polyvalent metal cation is greater than 0.2 to 2moles/100 gm of polymer, or such as from 0.3 to 1.75 moles/100 gm ofpolymer, or such as from 0.4 to 1.5 moles/100 gm of polymer.

Optionally, antioxidants may be included in the second component tostabilize the color or shade change to ambient radiation. Theantioxidants are believed to arrest the oxidation of color formers whenthe compositions are exposed to ambient radiation. Arresting theoxidation of the color formers inhibits further color or shade changefrom ambient radiation. Accordingly, a color or shade contrast betweenthe portions of the composition marked by exposure to low intensityenergy, such as by a laser, and the portions not exposed to the lowintensity energy, but only to ambient radiation, are maintained orstabilized. Any suitable antioxidant which arrests the oxidation ofcolor formers may be used. Examples of such antioxidants are hinderedphenols and hindered amines.

Hindered phenols include one or two sterically bulky groups bonded tothe carbon atom or atoms contiguous to the hydroxyl group-bonded carbonatom to sterically hinder the hydroxyl group. Examples of such hinderedphenols are 2,6-di-tert-butyl-4-methylphenol,2,2′-methylene-bis(4-methyl-6-tertbutylphenol),2,6-methylene-bis(2-hydroxy-3-tert-butyl-5-methyl-phenyl)4-methylphenol,2,2′-methylene-bis(4-ethyl-6-tert-butylphenol),2,6-bis(2′-hydroxy-3′-tert-butyl-5′-methylbenzyl)4-methyl-phenol,2,4,4-trimethylphenyl-bis(2-hydroxy-3,5-dimethylphenyl)methane,2,2′-methylene-bis[4-methyl-6-(1-methylcyclohexyl)]phenol,2,5-di-tert-butyl-4-methoxyphenol,4,4′-butylidenebis(6-tert-butyl-3-methyl-phenol), and1,1,3-tris(2-methyl-4-hydroxy-5-tertbutyl-phenyl)butane.

Hindered amines include one or two sterically bulky groups bonded to thecarbon atom or atoms adjacent to a nitrogen atom to sterically hinderthe nitrogen. The nitrogen itself may have bulky groups bonded to it.Examples of suitable hindered amines include2,2,6,6-tetraalkylpiperidine compounds including N-substituted2,2,6,6-tetraalkylpiperidine compounds. Such compounds contain a grouphaving a formula:

where R₁₈ hydrogen, (C₁-C₁₈)alkyl, (C₁-C₆)hydroxyalkyl, cyanomethyl,(C₃-C₈)alkenyl, (C₃-C₈)alkynyl, (C₇-C₁₂)aralkyl which may beunsubstituted or substituted in the alky moiety by hydroxyl,(C₁-C₈)alkanoyl or (C₃-C₅)alkenoyl; and R₁₉ is hydrogen or methyl.

The antioxidants may be micro-encapsulated in any suitable microcapsuleformulation and by any suitable micro-encapsulating method. Themicrocapsule prevents mutual contact of the antioxidant contained in themicrocapsule with the other materials outside of the microcapsule by theisolating action of the microcapsule wall at room and storagetemperatures. The microcapsules have increased permeability of theircontents upon application of sufficient heat or pressure. Permeation maybe controlled by selecting suitable microcapsule wall materials andmicrocapsule core materials. Examples of suitable wall materials includepolyurethanes, polyureas, polyamides, polyesters, polycarbonates andcombinations thereof. Typically, polyurethanes and polyureas are used tomake the microcapsule wall.

The microcapsules may be formed by emulsifying the core materialcontaining the antioxidant and subsequently forming a wall around dropsof the emulsified core material. In preparation of the microcapsule, areactant which forms the wall is added to the inside or outside of thedrops. Specific procedures for forming microcapsules are described, forexample, in U.S. Pat. No. 3,726,804, U.S. Pat. No. 3,796,696, U.S. Pat.No. 4,962,009, and U.S. Pat. No. 5,244,769.

Solvents suitable for forming the emulsion with the antioxidant include,but are not limited to, organic compounds such as phosphoric acidesters, phthalic acid esters, (meth)acrylic acid esters, othercarboxylic acid esters, fatty acid amides, alkylated biphenyls,alkylated terphenyls, alkylated naphthalenes, diarylethanes, chlorinatedparaffins, and mixtures thereof.

Auxiliary solvents may be added to the above-described organic solvents.Such solvents include, but are not limited to, ethyl acetate, isopropylacetate, butyl acetate, methylene chloride, cyclohexanone, and mixturesthereof.

Protective colloids or surface active agents may be added to the aqueousphase for stabilizing the emulsified drops. Water-soluble polymers maybe used as the protective colloids. An example of a suitablewater-soluble polymer is carboxyl-modified polyvinyl alcohol.

The size of the microcapsules may vary in size. Typically, themicrocapsules have an average diameter of 0.5 μm to 15 μm, or such asfrom 0.75 μm to 10 μm, or such as from 1 μm to 5 μm.

Optionally, one or more chain transfer agents may be used in the secondcomponent. Such chain transfer agents function as accelerators. Chaintransfer agents or accelerators increase the rate at which the color orshade change occurs after exposure of energy. Any compound whichaccelerates the rate of color or shade change may be used. Acceleratorsmay be included in the second component in amounts of from 0.01 wt % to25 wt %, or such as from 0.5 wt % to 10 wt %. Suitable acceleratorsinclude, but are not limited to, onium salts, and amines.

Suitable onium salts include, but are not limited to, onium salts inwhich the onium cation is iodonium or sulfonium such as onium salts ofarylsulfonyloxybenzenesulfonate anions, phosphonium, oxysulfoxonium,oxysulfonium, sulfoxonium, ammonium, diazonium, selononium, arsonium,and N-substituted N-heterocyclic onium in which N is substituted with asubstituted or unsubstituted saturated or unsaturated alkyl or arylgroup.

The anion of the onium salts may be, for example, chloride, or anon-nucleophilic anion such as tetrafluoroborate, hexafluorophosphate,hexafluoroarsenate, hexafluoroantimonate, triflate,tetrakis-(pentafluorophosphate) borate, pentafluoroethyl sulfonate,p-methyl-benzyl sulfonate, ethylsulfonate, trifluoromethyl acetate andpentafluoroethyl acetate.

Examples of typical onium salts are diphenyl iodonium chloride,diphenyliodonium hexafluorophosphate, diphenyl iodoniumhexafluoroantimonate, 4,4′-dicumyliodonium chloride, dicumyliodoniumhexafluorophosphate, N-methoxy-a-picolinium-p-toluene sulfonate,4-methoxybenzene-diazonium tetrafluoroborate,4,4′-bis-dodecylphenyliodonium-hexafluoro phosphate,2-cyanoethyl-triphenylphosphonium chloride,bis-[4-diphenylsulfonionphenyl]sulfide-bis-hexafluoro phosphate,bis-4-dodecylphenyliodonium hexafluoroantimonate and triphenylsulfoniumhexafluoroantimonate.

Suitable amines include, but are not limited to primary, secondary andtertiary amines such as methylamine, diethylamine, triethylamine,heterocyclic amines such as pyridine and piperidine, aromatic aminessuch as aniline and n-phenyl glycine, quaternary ammonium halides suchas tetraethylammonium fluoride, and quaternary ammonium hydroxides suchas tetraethylammonium hydroxide. The triethanolamines of formula IIIalso have accelerator activity.

Plasticizers also may be included in the second component. Any suitableplasticizer may be employed. Plasticizers may be included in amounts offrom 0.5 wt % to 15 wt %, or such as from 1 wt % to 10 wt % of thesecond component. Suitable plasticizers include, but are not limited to,phthalate esters such as dibutylphthalate, diheptylphthalate,dioctylphthalate and diallylphthalate, glycols such as polyethyleneglycol and polypropylene glycol, glycol esters such as triethyleneglycol diacetate, tetraethylene glycol diacetate, and dipropylene glycoldibenzoate, phosphate esters such as tricresylphosphate,triphenylphosphate, amides such as p-toluenesulfoneamide,benzenesulfoneamide, N-n-butylacetoneamide, aliphatic dibasic acidesters such as diisobutyl-adipate, dioctyladipate, dimethylsebacate,dioctylazelate, dibutylmalate, triethylcitrate,tri-n-butylacetylcitrate, butyl-laurate,dioctyl-4,5-diepoxycyclohexane-1,2-dicarboxylate, and glycerinetriacetylesters.

One or more flow agents also may be included in the second component.Flow agents may be included in amounts of from 0.05 wt % to 5 wt % orsuch as from 0.1 wt % to 2 wt % of the second component. Suitable flowagents include, but are not limited to, copolymers of alkylacrylates. Anexample of such alkylacrylates is a copolymer of ethyl acrylate and2-ethylhexyl acrylate.

Optionally, one or more organic acids may be employed in the secondcomponent. Organic acids may be used in amounts of from 0.01 wt % to 5wt %, or such as from 0.5 wt % to 2 wt %. Suitable organic acidsinclude, but are not limited to, formic acid, acetic acid, propionicacid, butyric acid, valeric acid, caproic acid, caprylic acid, capricacid, lauric acid, phenylacetic acid, benzoic acid, phthalic acid,isophthalic acid, terephthalic acid, adipic acid, 2-ethylhexanoic acid,isobutyric acid, 2-methylbutyric acid, 2-propylheptanoic acid,2-phenylpropionic acid, 2-(p-isobutylphenyl)propionic acid, and2-(6-methoxy-2-naphthyl)propionic acid.

Optionally, one or more non-ionic and ionic surfactants may be used.Surfactants may be included in the compositions in amounts of from 0.5wt % to 10 wt %, or such as from 1 wt % to 5 wt % of the component.Suitable non-ionic surfactants include, but are not limited to,polyethylene oxide ethers, derivatives of polyethylene oxides, aromaticethoxylates, acetylenic ethylene oxides and block copolymers of ethyleneoxide and propylene oxide. Suitable ionic surfactants include, but arenot limited to, alkali metal, alkaline earth metal, ammonium, andalkanol ammonium salts of alkyl sulfates, alkyl ethoxy sulfates, andalkyl benzene sulfonates.

Thickeners may be included in conventional amounts. Any suitablethickener may be incorporated in the components. Typically, thickenersrange from 0.05 wt % to 10 wt %, or such as from 1 wt % to 5 wt %.Suitable thickeners include, but are not limited to, low molecularweight polyurethanes such as having at least three hydrophobic groupsinterconnected by hydrophilic polyether groups. The molecular weight ofsuch thickeners ranges from 10,000 to 200,000. Other suitable thickenersinclude hydrophobically modified alkali soluble emulsions,hydrophobically modified hydroxyethyl cellulose and hydrophobicallymodified polyacrylamides.

Rheology modifiers may be included in the components in conventionalamounts. Typically rheology modifiers are used in amounts of from 0.5 wt% to 20 wt %, or such as from 5 wt % to 15 wt %. Rheology modifiersinclude, but are not limited to, vinyl aromatic polymers and acrylicpolymers.

Diluents may be included to provide a vehicle or carrier for thecomponents. Diluents are added as needed. Solid diluents or fillers aretypically added in amounts to bring the dry weight of the components to100 wt %. Solid diluents include, but are not limited to, celluloses.Liquid diluents or solvents are employed to make solutions, suspensions,dispersions or emulsions of the components. The solvents may be aqueousor organic, or mixtures thereof. Organic solvents include, but are notlimited to, alcohols such as methyl, ethyl and isopropyl alcohol,diisopropyl ether, diethylene glycol dimethyl ether, 1,4-dioxane,terahydrofuran or 1,2-dimethoxy propane, and ester such asbutyrolactone, ethylene glycol carbonate and propylene glycol carbonate,an ether ester such as methoxyethyl acetate, ethoxyethyl acetate,1-methoxypropyl-2-acetate, 2-methoxypropyl-1-acetate,1-ethoxypropyl-2-acetate and 2-ethoxypropyl-1-acetate, ketones such asacetone and methylethyl ketone, nitriles such as acetonitrile,propionitrile and methoxypropionitrile, sulfones such as sulfolan,dimethylsulfone and diethylsulfone, and phosphoric acid esters such astrimethyl phosphate and triethyl phosphate. Solvents also includecoalescing solvents such as ethers. Examples of such ethers includeethylene glycol phenyl ether and tripropylene glycol n-butyl ether.

Additional optional additives which may be included in the componentsinclude, but are not limited to, defoaming agents, coalescing monomers,preservatives and mold inhibitors. They are included in conventionalamounts.

The first and second components of the imaging compositions may beprepared by any suitable method. One method is to solubilize or dispersethe water-insoluble imaging compounds and other water-insolublecompounds in a coalescing solvent. Any solvent which disperses orsolubilizes the water-insoluble imaging compounds may be used. Suchcoalescing solvents include, but are not limited to, ester alcohols andglycol ethers. The solution or dispersion is then emulsified with anaqueous base portion containing polymer binders and other water-solublecompounds. Conventional emulsification methods may be used to prepareoil in water emulsions.

The components of the imaging compositions may be in the form of aconcentrate. In such concentrates, the solids content may range from 80wt % to 98 wt %, or such as from 85 wt % to 95 wt %. Concentrates may bediluted with water, one or more organic solvents, or a mixture of waterand one or more organic solvents. Concentrates may be diluted such thatthe solids content ranges from 5 wt % to less than 80 wt %, or such asfrom 10 wt % to 70 wt %, or such as from 20 wt % to 60 wt %.

The imaging compositions may be applied to a work piece by any suitablemethod. Such methods include, but are not limited to, spray coating,brushing, roller coating, ink jetting, dipping and immersion.

Upon application of a sufficient amount of energy to the imagingcompositions, a photofugitive or a phototropic response occurs. Theamount of energy may be from 0.2 mJ/cm² and greater, or such as from 0.2mJ/cm² to 100 mJ/cm², or such as from 2 mJ/cm² to 40 mJ/cm², or such asfrom 5 mJ/cm² to 30 mJ/cm².

The second component of the imaging compositions undergoes color orshade changes with the application of intensities of 5 mW of energy orless (i.e., greater than 0 mW), or such as from less than 5 mW to 0.01mW, or such as from 4 mW to 0.05 mW, or such as from 3 mW to 0.1 mW, orsuch as from 2 mW to 0.25 mW or such as from 1 mW to 0.5 mW. Typically,such intensities are generated with light sources in the visible range.Other photosensitizers and energy sensitive compounds, which may beincluded in the second component of the imaging compositions, may elicita color or shade change upon exposure to energy from light outside thevisible range. Such photosensitizers and energy sensitive compounds areincluded to provide a more pronounced color or shade contrast with thatof the response caused by the application of 5 mW or less. Typicallyphotosensitizers and energy sensitive compounds, which form the color orshade contrast with photosensitizers activated by energy at intensitiesof 5 mW or less, elicit a phototropic response.

While not being bound by theory, one or more color or shade changingmechanisms are believed involved to provide a color or shade changeafter energy is applied. For example, when a photofugitive response isinduced, the one or more sensitizers release a free radical to activatethe one or more photoreducing agents to reduce the one or moresensitizers to affect the color or shade change in the composition. Whena phototropic response is induced, for example, free radicals from oneor more sensitizers induce a redox reaction between one or moreleuco-type compounds and one or more oxidizing agents to affect thecolor or shade change. Some formulations have combinations ofphotofugitive and phototropic responses. For example, exposing acomposition to artificial energy, i.e., laser light, generates a freeradical from one or more sensitizers which then activates one or morephotoreducing agents to reduce the sensitizer to cause a photofugitiveresponse, and then exposing the same composition to ambient light tocause one or more oxidizing agents to oxidize one or more leuco-typecompounds.

Any suitable energy source may be used to induce the photofugitive orphototropic response. Examples of suitable energy sources include, butare not limited to, lasers, including lasers generated from hand heldlasers and 3-D imaging systems, and flash lamps. Operating wavelengthsof lasers may range from IR through UV. An example of a suitable laseris a neodymium (Nd) doped YAG laser operating at frequencies of 473 nmand 532 nm.

The imaging compositions provide a rapid and efficient means of changingthe color or shade of a work piece or of placing an image on a workpiece. After the imaging composition is applied to a work piece, asufficient amount of energy is applied to the imaging composition tochange its color or shade. The energy may be applied selectively to theimaging compositions. Generally, the color or shade change is stable.The term “stable” means that the color or shade change lasts at least 10seconds, or such as from 20 minutes to 2 days, or such as from 30minutes to 8 hours. Certain formulations which are sensitive to light at473 nm are stable indefinitely under controlled conditions where bluelight is filtered.

The image may be used as a mark or indicator to drill holes forfasteners to join parts together, cutting portions of the work piece andmasking such as in the assembly of terrestrial vehicles such asautomobiles, trucks, terrestrial and amphibious military vehicles,aeronautical ships such as airplanes and interplanetary vessels, marinevessels such as ships and boats, and terrestrial structures such ashouses, buildings in general and furniture; and to form an outline formaking a logo or picture on parts of terrestrial vehicles, aeronauticalships, marine vessels, terrestrial structures, and textiles. Since thecompositions may be promptly applied to a work piece and the imagepromptly formed by application of energy to create color or shadecontrast, workers no longer need to work adjacent the work piece to marklaser beam images with hand-held ink markers or tape in the fabricationof articles. Accordingly, the problems of blocking laser beams caused byworkers using the hand-held markers and tape are eliminated.

Further, the reduction of human error increases the accuracy of marking.This is important when the marks are used to direct the alignment ofparts where accuracy in fabrication is critical to the reliable and safeoperation of the machine.

EXAMPLE 1 Imaging Composition

A primer or first component of the imaging composition has a formula asdisclosed in Table 1 below. TABLE 1 Compounds Percent Weight Filmforming acrylic polymer binder 80 Zinc oxide 10 Cocoamphopropionate 5Ethylene glycol phenyl ether 1 Water 4

The acrylic polymer is a latex polymer which may be prepared by knownmethods in the art, or may be obtained commercially from Rohm and HaasCompany of Philidelphia, Pa. under the tradename RHOPLEX™ E-1801. Theliquid compounds are blended together at room temperature to form anemulsion. The zinc oxide particles with an average size of 1 μm are thenblended with the emulsion at room temperature to form a suspension. Thesuspension has a white appearance due to the zinc oxide pigment.

The second component or photosensitive component has a formula asdisclosed in Table 2 below. The compounds are combined at roomtemperature under red light. TABLE 2 Compounds Weight Percent Copolymerof styrene and acrylic acid 25 Calcium carbonate 20Cyclopentanone-2,5-bis[[4- 0.5 (diethylamino)phenyl]methylene]- LeucoCrystal Violet 1 o-chloro-hexaarylbiimidazole 6.5 1,2-naphoquinone 0.5Triethanolamine triacetate 1.5 Polyalkyl betaine polysiloxane copolymer2 Ester alcohol 8 Water 35

Copolymers of styrene and acrylic acid are known and methods forpreparing them may be found in the literature. They also arecommercially available from Rohm and Haas Company under the tradenameRHOPLEX™ P-376. The copolymer is mixed in water with the polyalkylbetaine polysiloxane copolymer to form an aqueous suspension. Calciumcarbonate is added to the suspension to maintain a pH of 8 to 11.

The imaging compounds: leuco crystal violet,o-chloro-hexaarylbiimidazole, 1,2-naphthaquinone, triethanolaminetriacetate andcyclopentanone-2,5-bis[[4-(diethylamino)phenyl]methylene]-are mixedtogether in the ester alcohol to form an organic solution. Acommercially available ester alcohol is TEXANOL™, which is availablefrom Eastman Chemical Co., Kingsport, Tenn. The aqueous suspension isemulsified with the organic solution using a conventional emulsifier toform an oil in water emulsion.

The primer is spray coated on a surface of an aluminum airplane bodywhich is coated with an epoxy primer designated as BR127 manufacturedand sold by American Cyanamide Corporation. The epoxy primer gives thealuminum surface a dark green appearance. The primer described in Table1 provides a white contrast with the dark green aluminum surface.

The second component or photosensitive component is spray coated on thefirst component. The second component is amber in appearance. Theworkers selectively form a pattern of cross-marks on the imagingcomposition with a 532 nm green light laser at 5 mW to designate whereholes are to be drilled for fasteners. The points on the photosensitivelayer exposed to the laser turn from amber to a clear appearancerevealing the white primer underlayer. The white of the cross-marksprovides a clear contrast with the amber and dark green backgrounds suchthat workers may clearly determine where they are to drill the holes.After the holes are drilled the imaging composition is hand peeled fromthe aluminum surface and discarded. No developers or strippers are usedto remove the imaging composition.

There is no indication that any of the dyes such as the leuco crystalviolet or the cyclopentanone sensitizer dye leach out of the secondcomponent and into the epoxy primer. The red color characteristic ofsuch leaching is not observed. Additionally, the inclusion of the zincoxide pigment in the first component is expected to increase thephotospeed of the color change by a Δ=+0.5 to +1 as measured by areflection densitometer.

EXAMPLE 2 Imaging Composition

A primer or first component of an imaging composition is composed of thecompounds disclosed in Table 3 below. TABLE 3 Compounds Weight PercentVinyl acetate/acrylic copolymer emulsion 75 2-alkyl-2-imidazoline 4Titanium dioxide 10 Ethylene glycol phenyl ether 1 Water 10

The vinyl acetate/acrylic copolymer is known in the art and methods ofpreparing it are well known. Such copolymers are commercially availablefrom Rohm and Haas Company under the tradename ROVACE™ 661. Theimidazoline is mixed with the ethylene glycol to form a uniformsuspension and then added to the copolymer emulsion and mixed. Thismixture is then mixed with water to form a suspension. The tintaniumdioxide pigment with an average particle size of 0.51 μm is mixed withthe suspension to form a dispersion. The dispersion has a whiteappearance.

The following photosensitive component is prepared at room temperatureunder red light. TABLE 4 Component Weight Percent Vinyl acetate/acryliccopolymer emulsion 75 2-alkyl-2-imidazoline 2 Vinyl aromatic polymer 4Leuco Crystal Violet 1 Tribromo methyl phenyl sulfone 52′,4′,5′,7′-tetraiodo-3,4,5,6-tetrachlorofluorescein 1 disodium salt2,2′-methylene-bis(4-methyl-6-tertbutylphenol) 1 Ethylene glycol phenylether 1 Water 10

The copolymer, vinyl aromatic polymer, and the 2-alky-2-imidazoline aremixed in water to form an aqueous emulsion.

The imaging components: leuco crystal violet, tribromo methyl phenylsulfone, 2′,4′,5′,7′-tetraiodo-3,4,5,6-tetrachlorofluorescein disodiumsalt, and micro-encapsulated2,2′-methylene-bis(4-methyl-6-tertbutylphenol) are solubilized inethylene glycol phenyl ether to form an organic solution. The aqueousemulsion and the organic solution are mixed to form an oil in wateremulsion imaging composition.

The first component of the imaging composition is roller coated on asurface of an aluminum airplane fuselage and dried. The fuselage iscoated with BR127 epoxy primer which gives the aluminum surface a darkgreen color. The first component is white and provides a color contrastwith the aluminum surface.

The second component of the imaging composition is spray coated on thefirst component. The second component is translucent and the white firstcomponent is visible under the photosensitive second component. Thesecond component is then dried.

Workers selectively image an outline of a company logo on the secondcomponent of the imaging composition using a 3D, 532 nm Nd:YAG laser at5 mW. The outline on the second component turns purple and the whitebackground from the first component provides a sharp contrast betweenthe purple outline and the dark green aluminum surface such that workerscan readily distinguish the purple outline.

The imaging composition is scored along the purple outline and theportion within the outline is peeled from the fuselage and discardedleaving an exposed aluminum surface. The exposed aluminum is thenpainted to form the logo on the fuselage. The remainder of the imagingcomposition is then peeled from the fuselage and discarded. No developeror organic solvents are used to remove the imaging composition from thefuselage.

There is no indication of leaching of the dyes from the second componentinto the epoxy primer. No red color characteristic of such leaching isobserved. Additionally, the inclusion of the pigment in the firstcomponent is expected to increase the photospeed of the color change bya Δ=+0.5 to +1, as measured by a conventional reflection densitometer.

EXAMPLE 3 Comparative

The following composition is prepared at room temperature in an areahaving ambient light filtered of green light. TABLE 5 Component WeightPercent Copolymer of styrene and acrylic acid 70Sodium-N-coco-β-aminopropionate 4 Aluminum oxide 10 Aminotriarylmethanedye 2 Tripropylene glycol n-butyl ether 2 Tribromo methyl sulfone 0.5n-Phenyl glycine 0.5 Eosin B 1 Water 10

The sodium-N-coco-β-aminopropionate is mixed with the styrene andacrylic copolymer to form a suspension. The dye, eosin B, n-phenylglycine and sulfone are mixed together with tripropylene glycol n-butylether to form a second suspension. The two suspensions are mixed andthen water is added to the mixture to form an oil in water emulsion. Themixing process is done at room temperature.

The aluminum oxide pigment with an average particle size of 0.5 μm isadded to the oil in water emulsion and mixed to form a dispersion. Themixing is done at room temperature.

The photosensitive dispersion is then spray coated on an aluminum plate5 meters×5 meters. The aluminum plate is coated with a conventionalepoxy primer used in priming aluminum airplane fuselages prior topainting. After application of the photosensitive dispersion to theprimed aluminum plate, the interface between the aluminum plate and thephotosensitive dispersion begins to turn a red color. The red colorexpands across the aluminum and also into the imaging composition. Thisundesired color change compromises the color or shade contrast betweenthe portions of the imaging composition exposed to laser light and thealuminum plate. Accordingly, workers find it difficult to locate themarks formed on the imaging composition indicating the marks formodification of the aluminum plate. The red color is believed to becaused by the sensitizer dye eosin B leaching into the epoxy primer onthe aluminum plate.

A primer having a formulation disclosed in the table below is prepared.TABLE 6 Compound Percent Weight Copolymer of styrene and acrylic acid 80Sodium-N-coco-β-aminopropionate 2 Tripropylene glycol n-butyl ether 3Aluminum oxide 10 Water 5

The primer is prepared by mixing the copolymer,sodium-N-coco-β-aminopropionate and tripropylene glycol n-butyl ether toform a suspension. Aluminum oxide is added to the suspension followed bymixing in a conventional sonic mixer with water added during theprocess. The mixing is done at room temperature.

A photosensitive component is prepared as described in Table 5 above,except that the aluminum oxide pigment is excluded in the formulation.Water is added to the component to make up the weight difference andbring the component to 100 wt %.

The primer described in Table 6 is roller coated on a 5 meters×5 metersaluminum plate which is coated with an epoxy primer used in primingaluminum airplane fuselages prior to applying paint. The primer is driedand presents a white contrast with the dark green of the primer coatedaluminum plate.

The photosensitive component is spray coated over the primer of Table 6to form an imaging composition on the aluminum plate. The photosensitivecomponent is dried over the primer or first component. Thephotosensitive component is translucent and the white underlying primeris visible creating a color contrast between the imaging composition andthe dark green aluminum plate. No red color is observed forming on thealuminum or in the imaging composition. Accordingly, the eosin Bsensitizer dye is not believed to be leaching from the photosensitivecomponent.

A 532 nm laser at 5 mW is used to selectively affect a color change inthe imaging composition with cross-marks. The color of the cross-marksis purple and presents a clear, visible contrast with the whitebackground of the unexposed portions of the imaging composition and thedark green aluminum plate. Accordingly, workers can readily modify thealuminum plate based on the purple cross-marks.

In addition to preventing the sensitizer dye from leaching into theepoxy primer on the aluminum plate, and presenting improved colorcontrast over the photosensitive component, the imaging composition isexpected to have an increased photospeed by a Δ=+0.5 to +1, as measuredby a reflection densitometer.

1. An imaging composition comprising a first component comprising one ormore opacifying compounds, and a second component comprising one or moresensitizers.
 2. The imaging composition of claim 1, wherein the one ormore opacifying compounds are chosen from pigments, metal salts, silica,silicates and clays.
 3. The imaging composition of claim 1, wherein theone or more sensitizers are chosen from xanthene compounds andcyclopentanone based conjugated compounds.
 4. The imaging composition ofclaim 1, wherein the first component further comprises one or moreadhesives.
 5. The imaging composition of claim 1, wherein the secondcomponent further comprises one or more color formers.
 6. The imagingcomposition of claim 1, wherein the second component further comprisesone or more micro-encapsulated antioxidants.
 7. An imaging compositioncomprising a first component comprising one or more opacifying compoundsand one or more release agents, and a second component comprising one ormore sensitizers and one or more release agents.
 8. A method comprising:a) providing a first component of an imaging composition, the firstcomponent comprises one or more opacifying compounds; b) applying thefirst component of the imaging composition to a work piece; c) providinga second component of the imaging composition, the second componentcomprises one or more sensitizers; d) applying the second component ofthe imaging composition on the first component; e) applying energy tothe imaging composition at powers of 5 mW or less to affect a color orshade change in the second component of the imaging composition; and f)executing a task on the work piece as directed by the color or shadechange of the second component of the imaging composition to modify thework piece.
 9. The method of claim 8, further comprising the step ofremoving the imaging composition from the work piece by peeling theimaging composition from the workpiece.
 10. The method of claim 8,wherein the work piece is chosen from a terrestrial vehicle, anaeronautical ship, a marine vessel, a terrestrial structure, and atextile.